Radio frequency apparatus



Nov. 15, 1966 R. G. LOCK 3,286,125

RADIO FREQUENCY APPARATUS Filed Nov. 20, 1961 2 Sheets-Sheet 1 FIG.5.

INVENTORI RICHARD G. LOCK,

HIS ATTORNEY.

NOV. 15, 1966 LOCK 3,286,125

RADIO FREQUENCY APPARATUS Filed Nov. 20, 1961 2 Sheets-Sheet 2 FIGZJINVENTORI RICHARD G. LOCK BWW HIS ATTORNEY.

United States Patent RADIO FREQUENCY APPARATUS Richard G. Lock, Albany,N.Y., asslgnor to General Electric Company, a corporation of New YorkFiled Nov. 20, 1961, Ser. No. 153,425 4 Claims. (Cl. 31539.63)

My invention relates to improved interdigital magnetron devices whichare particularly adapted for anode voltage tuning and to improved radiofrequency apparatus incorporating such devices.

A magnetron is a microwave device employing crossed electric andmagnetic fields between concentrically arranged electrodes. In the caseof interdigital voltage tunable magnetrons, the types, for example,disclosed and claimed in US. Patents Nos. 2,810,095 and 2,810,096 of P.H. Peters, Jr., et al., issued October 15, 1957, and assigned to thesame assignee as the present invention, the anode comprises a pluralityof interdigital segments and adjacent segments are connected alternatelyto two axially spaced terminals sealed in the envelopes of the devices.For 71' modeoperation of this type of device, each terminal is a radiofrequency equipotential and it is usually des'irable to connect thesetwo terminals directly to a transmission line by mounting the tubedirectly in theline,

One such form of apparatus is disclosed and claimed in U.S. Patent No.2,940,007 of H. L. Thal, Jr., issued June 7, 1960, and also assigned tothe same assignee as the present invention. This form of apparatusprovides for a RF. transformer, or transition, section between thedevice and a coaxial line and generally requires for high frequencyoperation at least some form of auxiliary R.F. shielding structure toavoid undesired radiation. It is desirable to provide an interdigitaltube structure and RF. apparatus which enables a direct connectionbetween a coaxial, or other form of unbalanced transmission line,thereby to avoid the necessity for a transition section between the tubeand line. Also, it is desirable that the circuit comprises a closedstructure thereby to prevent RF. radiation and to obviate the need forauxiliary RF. shielding. Coaxial contact arrangements coextensive withthe longitudinal axis of the tube have been suggested. However, thisform of structure can introduce undesired coupling with the cathodeassembly which generally includes a nonemissive cathode, an electronemitter, and control means. Also, this form of structure usually isprovided with DC. contacts at either or both ends of the magnetron andcan interfere with the location and close spacing of magnet pole piecesrequired to provide an operating magnetic field extending coaxiallythrough the device.

The present invention contemplates a new and improved interdigitalmagnetron structure and RF. apparatus incorporating such a structure andwhich is noncoaxial with respect to the magnetron and is adapted forproviding a closed structure effective to minimize R.F. radiation, toobviate the need for auxiliary shielding structure to avoid undesirablecoupling with the cathode assembly and to avoid interference with thepositioning and spacing of the operating magnet pole pieces.

Accordingly, the primary object of my invention is to provide a new andimproved interdigital magnetron device which is particularly adapted fordirect connection to an unbalanced transmission line.

Another object of my invention is to provide a new and improvedinterdigital magnetron device and new and improved R.F. circuitapparatus particularly adapted for incorporating such a device.

Another object of my invention is to provide a new and improvedinterdigital magnetron device and.R.F. circuit apparatus adapted forenabling direct connection between the magnetron and an unbalancedtransmission line and which obviates the need for auxiliary R.F.shielding structure. I

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out without particularity inthe claims annexed to, and forming part of this specification.

In carrying out the objects of my invention I provide an interdigitalmagnetron comprising an envelope having three ringeshaped anodeterminals sealed in axially spaced relation in the wall of the envelope.Provided in the envelope is an annular interaction region defined by anelongated centrally-disposed nonemissive cathode and a plurality ofinterdigital anode segments arranged in a cylindrical array. The anodesegments comprise two sets of alternate segments Thesegments of one setare connected between and are supported by the outer two of theaforementioned three axially spaced anode terminals. The segments of theother set are connected and are supported by the intermediate anodeterminal. An electron emitter and control means therefor are provided inthe device at a location axially displaced from the interaction regionand are adapted for directing electrons into the interaction region.Provided for cooperating with the device is an RF. output circuitcomprising an unbalanced transmission line of either the coaxial type orthe type including a single conductor between two parallel planes. Inthis apparatus the inner conductor is directly connected to theintermediateanode terminal and opposed sides of the outer conductor ofthe coaxial line, or the two outer planar conductors of the wire betweentwo planes type of line, if the latter is being used, are directlyconnected to both of the outer anode terminals. In one form of theinvention, the opposed sides of the outer conductor of the coaxial line,or the two outer planar conductors of the wire between two planes typeof line, are apertured to include registering openings to receive theends of the device and make circumferential contact to both outer anodeterminals. This arrangement provides a closed structure to prevent R.F.radiation. Additionally, in this form of structure a tuning element canbe slidably positionable in an extension of the line and connecting theconductors on one side of the device.

For a better understanding of my invention reference may be had to theaccompanying drawing in which:

FIGURE 1 is an enlarged sectionalview of an interdigital magnetrondevice embodying my invention;

FIGURE 2 is a fragmentary exploded perspective view illustrating amanner of constructing the anode assembly incorporated in the deviceillustrated in FIGURE 1;

FIGURE 3 is a fragmentary view illustrating R.F. apparatus including myimproved magnetron device and a coaxial line R.F. output;

FIGURE 4 is a fragmentary view illustrating R.F. .apparatus including myimproved magnetron device and a wire between two planes type of lineoutput circuit;

FIGURE is a fragmentary partially sectionalized view of RF. apparatusincorporating my improved magnetron device and comprising a coaxial lineR.F. output circuit and tuning means; and

FIGURE 6 is a fragmentary partially sectionalized view of RF. apparatusincorporating my improved magnetron device and comprising wire betweentwo planes type of RF. output circuit and tuning means.

Referring to the drawing, there is shown in FIGURE 1 a magnetron deviceembodying a form of my invention and generally designated 1. The device1 includes an envelope generally designated 2 and constituted of astacked assembly of alternately arranged metal and ceramic memberswherein the metal members serve as electrical contacts'or terminals ofthe device and the ceramic members serve as insulative wall sections andspacers between the metal members. The mentioned metal members includethree ring-shaped anode terminals 3-5 separated by a pair of ceramiccylinders 6 of equal lengths. The metal members further include a frusto-conical control electrode 7 which includes a flanged, or annular,section 8 separated from the anode terminal 3 by a cylindrical ceramicmember 9.

The envelope 2 is completed by a pair of end ceramic members 10 and 11and a pair of metal end caps 12 and 13. The elements described to thispoint are suitably bonded together to provide a hermetically sealedevacuated envelope.

The end cap 13 carries a metal post 14 which comprises a cold, ornon-emitting, cathode extending coaxially in the envelope to a pointjust'inwardly of the inner end of the control electrode 7. The end cap12 carries a coaxial boss 15 on which is mounted one end of a helicalemitter 16. The other end of the emitter 16 is supported on and makeselectrical contact with the inner end of the cold cathode 14. In thisarrangement the end caps 12 and 13 serve as DC. cathode contacts foropposite ends of the emitter 16. This construction of the cold cathodeand emitter are substantially identical to those disclosed in theaforementioned Patents Nos. 2,810,095 and 2,810,096. However, it is tobe understood that this manner of cathode construction is not requiredfor operation of my presently disclosed invention. My invention isapplicable to interdigital magnetron devices including other forms ofcathode constructions such, for example, as the cathode constructiondisclosed and claimed in US. Patent No. 2,930,933 of G. J. Griffin, Jr.et al. issued March 29, 1961 and assigned to the same assignee as thepresent invention and which incorporates an emissive cathjode mountedfrom a single end of the tube envelope. Also, my invention is notlimited to directly-heated cathode structures but can incorporateindirectly-heated emitters of the type disclosed and claimed, forexample, in US. Patent No. 2,997,624 of P. H, Peters, Jr., issued August22, 1961 and assigned to the same assignee as the present invention. 7

As seen in FIGURES 1 and 2, the present device is of the interdigitaltype and the anode terminals support within the envelope 2 an anodeassembly including two sets of axially extending anode segmentsalternately arranged in a cylindrical array and supported concentricallyin the envelope by the anode terminals 3-5. More specifically, alternatesegments, or the segments of one set of alternate segments, arebail-like in construction and are conductively connected to andsupported by the inner rim portions of the two outer anode terminals 3and 5. The other segments 18, or the segments of the other set ofalternate segments, are straight elongated segments and are conductivelyconnected at the midportions thereof to, and are supported by, the innerrim portion of the intermediate anode terminal 4. As seen in FIGURE 2,the one set of alternate segments of the just described anode assemblygenerally designated 17 can be conveniently provided by forming, as bybobbing, each of the outer anode terminals 3 and 5 to include aplurality of equally, circumferentially spaced and longitudinallyextending L-shaped half-segments 19 which, when the device is assembled,are joined at the adjacent inner ends thereof to provide theabove-mentioned bail-like segments 17 interconnecting the terminals 3and 5. Also, the other set of segments 18 can be conveniently formed byconstructing the inner anode terminal 4 of a pair of joined back-to-backrings with oppositely extending L- shaped half-segments 20 which, whenthe just-mentioned rings are joined together, form the equally,circumferentially spaced and generally T-shaped anode segments 18extending interdigitally between the segments 17 carried by the anodeterminals 3 and 5. The segments of the difierent sets are slightlyseparated circumferentially to provide axially extending interactiongaps. Also, the segments are slightly spaced radially from the coldcathode 14 to provide an annular space charge interaction region. As iswell understood in the magnetron art, it is the interaction between thehigh frequency fields across thesegment gaps and the rotating andbunched space charge in the interaction region that effects the desiredenergy transfer from the space charge to the oscillatory circuit of theanode.' As is also well understood in the art, the electron rotationresults from the provision of an operating magnetic field extendingcoaxially through the device. Such a field is usually provided bydisposing the magnetron between opposed closely spaced pole piecesdesignated N and S of a magnet in the manner illustrated in the variousfigures in the drawing.

In the embodiment illustrated, the electrons constituting the rotatingbeam originate in the device at the emitter 16 which is longitudinallydisplaced relative to the interaction region defined by the cold cathodeand anode segments, and the introduction or injection of the electronsinto the interaction region is under control of the frusto-conicalelectrode 7. This feature of the disclosed structure does not constitutepart of the present invention but is disclosed and claimed in theaforemen tioned Patent 2,810,096. In 'Ir-IllOdS operation of theabove-described device, the outer anode terminals 3 and 5 are of thesame R.F. potential and the inner terminal 4 is out of phase therewith.Thus, and as seen in FIGURES 3-6, the device 1 is particularly welladapted for having directly connected thereto an unbalanced transmissionline of either the coaxial or wire between two planes types.

' In FIGURE 3 is illustrated an RF. apparatus, or voltage tunablemagnetron R.F. apparatus, comprising a tube 1 "and a directly connectedcoaxial transmission line 21. In this apparatus the inner conductor 22of the line 21 is directly connected to the inner anode terminal 4 andthe outer conductor 23 which is cylindrical is directly connected toboth of the outer anode rings 3 and 5 at diametrically opposed points onthe end of the conductor 23. Thus, the connection between the device 1and the output line 21 is eflected without the need for a transitionsection or a substantial open region which would require R.F. shieldingat high frequencies.

The apparatus of FIGURE 4 is similar to that of FIGURE 3 except that inplace of a coaxial transmission line, the RF. output circuit compriseswire between two planes type of line 24 specifically including spacedplanar outer conductors 25 connected each to one of the outer anodeterminals 3 and 5 of a device 1, and an intermediate spaced parallelinner conductor or wire 26 conductively connected to the inner anodeterminal 4.

Illustrated in FIGURE 5 is apparatus incorporating a device 1 and acompletely enclosed R.F. output circuit generally designated 27. In thisembodiment the output circuit'comprises a coaxial line including aninner conductor 28 and a tubular outer conductor 29. The inner conductor28 is in two sections with each section conductively connected to theintermediate anode terminal 4 on an opposite side of the. device 2. Theouter conductor 29 includes a cylindrical section 30 and a generallyflat tened tubular transition section 31. The flattened section 31 hasopposed planar walls or sides which are generally coextensive with theanode terminals 3 and 5 and are formed to include a pair of opposedregistering apertures 32. The device 1 is positioned in the section 31and the lowermost anode terminal 5 is seated in an annular recess 33formed on the inner surface of the lower side of th section 31 and so asto be concentric with the aperture 32. Thus, the lower side of thesection 31 makes circumferential conductive contact with the anodeterminal 5. The uppermost anode terminal 3 is generally coplanar withthe upper side of the section 31 and a retaining ring 34 is provided forholding the device 1 securely positioned in the section 31 with theanode ring 3 making suitable circumferential contact with the upper sideof the section 31. In this manner I have provided an apparatus includingan RF. output which is completely enclosed by conductive material and,thus, is not subject to undesired R.F. radiation. This renders thedescribed structure particularly effective for high frequencyapplications where R.F. shielding is generally required.

As also seen in FIGURE 5, the section 31 comprises a tubular functionalregion generally designated 35 located opposite the output region 27.Region 35 contains one section, or a continuation, of the centerconductor 28. Also, ahe region 35 can contain an element or stub 36slidably fitted over the center conductor and connecting the centerconductor and the outer conductor. The element 36 can be provided with ahandle 36a and is adapted for being used for adjustably resonating theapparatus at predetermined desired operating frequencies.

Illustrated in FIGURE 6 is apparatus including a device 1 and apartially closed R.F. output circuit generally designated 37. In thisembodiment the RF. output comprises a section of wire between two planestype of line 38 and includes a pair of spaced parallel planar outerconductors 39 and a spaced parallel inner conductor or wire 40. Theinner conductor 40 is in two sections each conductively coupled directlyto one side of the inner anode ring 4 and the outer conductors 39include a section wherein the conductors are formed with registeringapertures 41. The device 1 is positioned in the apertured section andthe lowermost terminal 5 is seated in an annular recess 42 formed on theinner surface of the lower one of the planar conductors 39, and thusmakes circumferential conductive contact therewith. The uppermost anodeterminal 3 is generally coplanar with the upper one of the planarconductors 39 and a retaining ring 43 is effective for holding thedevice in one position securely in the apparatus with the anode ring 3making suitable circumferential conductive contact with the upperconductor of the line 38. Thus, is provided apparatus including an RF.output which has opposed planar conductors both at the same R.F.potential and serving to provide some measure of RF. shielding andminimize the amount of shielding required to insure against undesiredR.F. radiation.

The embodiment of FIGURE 6 is also adapted for adjustable tuning.Specifically, and as seen in FIGURE 6, the the line 38 includes afunctional region generally designated 44 disposed on the side of thedevice 1 opposite the RR output. In the region 44 there is provided astub or element 45 which is slidable over the center conductor 40 andinterconnects the center and outer conductors. Additionally, the element45 is provided with a handle 45a and is adjustably positionable relativeto the device 1 for thereby adjustably resonating the circuit atpredetermined desired operating frequencies.

While I have shown and discussed specific embodiments of my invention, Ido not desire my invention to be limited to the particular forms shownand described, and I intend by the appended claims to cover allmodifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Radio frequency apparatus comprising an electric discharge deviceincluding an envelope, an interaction structure contained in saidenvelope including a negative central electrode and a surroundingcylindrical array of circumferentially spaced anode segments, threeaxially spaced anode terminals sealed in the wall of said envelope withalternate ones of said anode segments connected to the outer two of saidterminals and the others of said segments connected to the intermediateone of said terminals and a radio frequency output transmission linecomprising a central conductor coupled to said intermediate terminal andouter conductive means coupled to both said outer anode terminals, saidtransmission line includes an output section and a tuning sectionlocated on opposite sides of said device and said tuning sectionincludes an element interconnecting the central conductor and outerconductive means and is adjustably positionable for selectivelyadjustably resonating said apparatus.

2. Radio frequency apparatus comprising an electric discharge deviceincluding an envelope, an interaction structure contained in saidenvelope including a negative central electrode and a surrounding arrayof circumferentially spaced anode segments, three axially spacedringshaped anode terminals sealed in the wall of said envelope withalternate ones of said anode segments connected to the outer two of saidterminals and the others of said segments connected to the intermediateone of said terminals, and a radio frequency transmission linecomprising an output section including an inner conductor and a pair ofoppositely disposed planar conductive sections extending in spacedparallel relation to said inner conductor, said inner conductor beingcoupled to said intermediate terminal, and each said planar conductorbeing apertured and having rim portions thereof making circumferentialelectrical contact with one of said outer terminals of said device, saidtransmission line including a section extending on the side of saiddevice opposite said output section and further including an elementconductively interconmeeting the inner and planar conductors andslidably positionable for selectively adjustably resonating saidapparatus.

3. Radio frequency apparatus comprising an electric discharge deviceincluding an envelope, an interaction struc ture contained in saidenvelope including a negative central electrode and a surroundingcylindrical array of circumferentially spaced anode segments, threering-shaped axially spaced anode terminals sealed in the wall of saidenvelope with alternate ones of said anode segments connected to theouter two of said terminals and the other of said segments connected tothe intermediate one of said terminals, and -a coaxial transmission linecomprising an output section including a center conductor and a tubularouter conductor having a cylindrical section extending parallel to saidcenter conductor and a section having opposed planar walls, said centerconductor being 'coupled to said intermediate terminal, said opposedplanar walls of said outer conductor each being apertured and having arim portion thereof coupled to one of said outer terminals of saiddevice, said transmission line including a tuning section locatedopposite said output section and containing an element conductivelyinterconnecting said inner and outer conductors and adjustablypositionable for selectively adjustably resonating said apparatus.

4. An interdigital anode assembly comprising in combination,

(a) a central anode ring assembly,

(b) said central anode ring assembly consisting of two planar rings eachof which have axially extending segments therefrom in one direction,

(c) said rings being placed in abutting back-to-back References Cited bythe Examiner UNITED STATES PATENTS Nordsieck 315--39.73 X Ludi 31539.73X

Peters 315-3913 McLaughlin 31539.73

HERMAN KARL SAALBACH, Primary Examiner. Q ARTHUR GAUSS, Examiner.

S. CHATMON, JR., Assistant Examiner.

1. RADIO FREQUENCY APPARATUS COMPRISING AN ELECTRIC DISCHARGE DEVICEINCLUDING AN ENVELOPE, AN INTERACTION STRUCTURE CONTAINED IN SAIDENVELOPE INCLUDING A NEGATIVE CENTRAL ELECTRODE AND A SURROUNDINGCYLINDRICAL ARRAY OF CIRCUMFERENTIALLY SPACED ANODE SEGMENTS, THREEAXIALLY SPACED ANODE TERMINALS SEALED IN THE WALL OF SAID ENVELOPE WITHALTERNATE ONES OF SAID ANODE SEGMENTS CONNECTED TO THE OUTER TWO OF SAIDTERMINALS AND THE OTHERS OF SAID SEGMENTS CONNECTED TO THE INTERMEDIATEONE OF SAID TERMINALS, AND A RADIO FREQUENCY OUTPUT TRANSMISSION LINECOMPRISING A CENTRAL CONDUCTOR COUPLED TO SAID INTERMEDIATE TERMINAL ANDOUTER CONDUCTIVE MEANS COUPLED TO BOTH SAID OUTER ANODE TERMINALS, SAIDTRANSMISSION LINE INCLUDES AN OUTPUT SECTION AND A TUNING SECTIONLOCATED ON OPPOSITE SIDES OF SAID DEVICE AND SAID TUNING SECTIONINCLUDES AN ELEMENT INTERCONNECTING THE CENTRAL CONDUCTOR AND OUTERCONDUCTIVE MEANS AND IS ADJUSTABLY POSITIONABLE FOR SELECTIVELYADJUSTABLY RESONATING SAID APPARATUS.